1. Field of the Invention
This invention relates to deodorant compositions, which are suitable for topical application to the human skin. In particular, it refers to propellant driven aerosol compositions which contain certain biguanide compounds.
2. The Related Art
Deodorant compositions suitable for topical application to the human skin, in particular the underarm area, have long been known. These typically comprise a deodorant active material, which may be an inorganic metal salt, such as an aluminium or zinc salt, in a cosmetically acceptable base. Alternatively the deodorant agent in the topical composition may be organic; two very popular and often used organic deodorant agents are ethanol and triclosan. For a propellant driven aerosol product, a base composition containing an appropriate deodorant agent is typically combined in an aerosol can with an appropriate amount of propellant.
Conventional propellant driven aerosol compositions of this form do have associated problems. The exact nature of the problem will vary according to the formulation and the deodorant agent used, but typical problems include insufficient deodorant efficacy, perfume interaction, or sensory problems such as the production of visible deposits.
It is known that certain biguanide salts can have antimicrobial activity. For example, polyhexamethylene biguanide hydrochloride (PHMB) salts have been sold by Zeneca for many years, for example as a 20% aqueous solution of the hydrochloride salt, under the tradename Cosmocil CQ, for purposes which include their use as antimicrobials. In addition, such an effect is described in "Disinfection, Sterilization, and Preservation", chapter 18(polymeric antimicrobial agents),fourth edition, Seymour S. Block, Lea & Febiger, 1991.
Such polyhexamethylene biguanide hydrochloride type materials are also known deodorant actives in their own right. For example in U.S. Pat. No. 4,478,821 (Gillette), the ability of PHMB salts to reduce body odour is described. According to the teaching therein, such salts are suitable for inclusion in any product form, including lotions, sticks, creams, ointments, powders, suspensions, soaps, gels, and pressurized aerosols. However it is noted that no propellant driven aerosol compositions are exemplified in this patent; instead the examples relate to liquid and stick formulations.
However, problems have been experienced in trying to incorporate hydrophilic, cationic polymer type materials, such as PHMB salts, into propellant driven aerosol formulations, to try to formulate compositions which would be suitable for commercial sale. In particular such salts have been found to be incompatible with aerosol formulations which comprise significant amounts of a non polar propellant, such as a hydrocarbon propellant, and short chain monohydric alcohol, such as ethanol.
If the neat PHMB salts are introduced into a hydrocarbon propellant/ethanol system, the salt does not appreciably dissolve. Attempts have been made to incorporate PHMB salts into propellant driven aerosols where the propellant is non polar, using surfactants. However, this has not been found to be an efficient way of dissolving or dispersing the salts into such aerosol compositions, since it has proved difficult to find a surfactant which was compatible with the short chain monohydric alcohol/non polar hydrocarbon vehicle, did not effect the chemical nature of the PHMB salt, and yet was suitable for use in a topical cosmetic composition.